The Four Sisters
The Four Sisters are the female soldiers employed by Rubeus that get the first crack at trying to capture Rini and defeat the Sailor Senshi. They are sort of like 'anti-senshi', if you will, in that their roles are similar to those of the senshi but instead of fighting for the common good, they carry out many missions to aid the villains. Each sister corresponds to a certain senshi (except for Sailor Moon, but she gets to slug Rubeus later on) and has similar powers and strength.
The Sisters' story has its beginnings in the early part of SMR. They first appeared in the past (20th century) with Rubeus to begin to carry out the mission, which was gaining Rini/the Silver Crystal and corrupting the city. This would thus alter the future. Their tactics involved taking over negative points and spreading the energy that came out of them in addition to trying to attract Rini so that they could nab her. They had all kinds of lackeys (the droids) to do most of the dirty work, though, but the droids kept getting killed off when they tried to defeat the senshi. This led to many confrontations between the senshi and the sisters, and to many thwarted missions. Eventually, Rubeus began to get impatient with them, because in addition to not being able to do their jobs, they bickered like hell over every trivial little thing. He finally began to 'fire' them, so to speak, by telling them off (rather rudely) and cutting them off from the mission. However, the senshi were there to pick them up and dust them off, and Sailor Moon ended up purifying them with her Silver Crystal.
Among other things, the Four Sisters have a love for cosmetics. That's why they decide to sell cosmetics to support themselves after Sailor Moon heals them. They end up sharing a rather nice studio apartment, which is seen later on when they re-appear in the episode where Sapphire dies. For more information, check out each individual sister's profile/story by clicking on the links or scrolling down to see them.
Avery is the second oldest sister and Sailor Venus' opposite. Up in the corner there you can see that she has her own little whip thing to counter the Venus Love-me Chain. Anyway, Avery is more than just a little vain, especially when it comes to beauty, and this constantly bothers her other sisters who compete with her to be beautiful. She irks Prizma when she makes a jab at her about not being able to get any dates with guys since they came to the 20th century (in the Japanese version, I hear that this is a jab about Prizma having gotten dumped just before they left) and she earns the nickname 'Prima Donna' from Rubeus, whom she also inadvertantly ticks off with her vanity. However, Avery draws the least amount of criticism from Rubeus, and it seems as though he has a thing for her. Although she likes him (all the sisters do), nothing ever develops.
Eventually, Rubeus begins to get impatient with Avery as well. Soon after Sailor Moon heals Catsy and Bertie, Rubeus hands down an ultimatum to both Avery and Prizma who, by then, are the only two sisters left, and tells them that they have one last chance to destroy the Sailor Senshi if they don't want to be disgraced. He gives them both this thing called a strobe (come on, it's a ball on a stick!), which will amplify their power. Prizma is the one who receives it, and it drives her mad. She tries to kill a terrified Avery, who realizes that they've both been had. When she sees how much better her other healed sisters are, she decides that she wants to be healed as well. Sailor Moon is more than happy to do the job.
Bertie is the second youngest of the Four Sisters and she is Sailor Mercury's opposite. Bertie isn't as vain or as arrogant as the other sisters, but she can still be mean. Anyway, Bertie is the brains of the group. She enjoys intellectual pursuits, like playing chess or reading books. She is not as wrapped up in flirting with Rubeus or in primping like the other sisters, but she still tries to look good.
Bertie ends up meeting with the senshi when she sabotages a chess match. Sailor Mercury is in the same match, and they end up facing off. Bertie threatens to destroy Sailor Mercury if she wins the match, but Mercury still manages to put her in check. Bertie's remaining sisters, already ticked at Catsy for her supposed betrayal, show up and asses the situation. They are quick to declare Bertie a failiure and disown her as well. She is crushed and starts to freeze everyone, out of retaliation. Catsy and Sailor Moon talk her down out of it ahd at Catsy's urging, Bertie accepts Sailor Moon's healing.
Catsy is the youngest sister and she is Sailor Mars' opposite. She strikes me as not having very high self-esteem. Catsy is the one who pioneers the idea of selling cosmetics, when she appears at Rei's temple in a disguise doing so. Apparently, Rei's temple was an energy point (something's always happening there...). Anyway, Catsy is madly in love with Rubeus but apparently, he can't stand her. Catsy would bend over backwards for Rubeus and she would do anything to please him because she wants him to love her. This is what he takes advantage of through cheap flattery. She doesn't strike me as having much self-confidence, though, because he berates her often and is absolutely cruel to her, yet she still keeps coming back in vain hopes that maybe she'll impress him one day. She never does, but in the end, it doesn't matter.
On one of the occasions that Catsy tries to impress Rubeus, she buys him a bottle of cologne that he ends up smashing. He sends her over to Rei's soon after, telling her she's got work to do there. So she goes, but she fails Rubeus by losing the Rabbit yet again. He shows up and basically tells her off, asking her to perform suicide because she is a disgrace. This is a major blow to her, and she begins to go ballistic and attack the senshi (who are now there) and Rei's little dopey temple helper-dude, Chad. When she attacks Chad, Rei jumps in front of him and this puzzles Catsy, who can't understand why Rei is willing to take Chad's beating. Rei declares that it's because Chad is someone she cares about and that she won't let him get hurt. Chad does likewise for Rei, and Rei does so for Catsy when Sailor Jupiter tries to pound her. By this time, Catsy is completely awestruck that someone would do that, especially for her, when SM offers to purify her. She accepts, and this signifies the start of the Four Sisters all getting healed.
Prizma is the oldest of the Four Sisters and is Sailor Jupiter's opposite. She is quite ruthless and strikes me (at least) as being rather cold. Like Sailor Jupiter, Prizma has had her share of boyfriend trouble. At one time Prizma was apparently dating Sapphire, according to Avery ("Prizma and Sapphire used to be an item"), but they broke up sometime just before she left to go to the 20th century with Rubeus and the other three sisters. However, Prizma still seems to have a soft spot for him, which is part of the reason why she takes him in when he is running around wounded in the 20th century.
Out of all the sisters, Prizma seems to be particularly spiteful toward Avery. It is implied throughout the series that Avery was the one who broke up Prizma and Sapphire. The two of them vie and compete with each other for almost everything, from what they wear to who gets to do the next mission. However, they often end up doing missions together, even though they fight and/or criticize each other over how the mission is done. Eventually Prizma, along with Avery, is given an ultimatum stating that they have one final chance to kill the Sailor Senshi. Prizma is given this thing called a strobe, which amplifies her power, but it ends up making her go crazy. Prizma accuses Avery of wanting to turn traitor, supposedly like the other sisters, and tries to kill her, but Avery is healed by Sailor Moon. She accuses the other sisters, who are there with Sailor Moon, of turning traitor right as Rubeus shows up and tells her off. This destroys her self-esteem and she tries to kill herself along with the other sisters (and senshi) by opening a vortex with the strobe. However, Sailor Moon destroys it, and seeing how much better her other healed sisters are doing (and how much they care for her), she lets Sailor Moon heal her.
Four Sisters Pictures: